Rapid Risk Assessment: Detection of new SARS-CoV-2 variants related to mink
This assessment considers the risk to human health posed by SARS-CoV-2 mink related variants. It is based on information available to ECDC at the time of publication and, unless otherwise stated, the assessment of risk refers to the risk that existed at the time of writing. It follows the ECDC rapid risk assessment methodology, with relevant adaptations. The overall risk is determined by a combination of the probability of an event occurring and its consequences (impact) for individuals or the population.
Since April 2020, when the first SARS-CoV-2 infection was reported in the Netherlands in a mink and subsequently in a mink farm worker, it has been established that human-to-mink and mink-to-human transmission can occur. Since then, infections in mink have been reported in Denmark, Italy, Spain, Sweden and the United States.
On 5 November 2020, Denmark reported 214 human COVID-19 cases infected with SARS-CoV-2 virus variants related to mink, as well as infected mink at more than 200 mink farms. Most human and animal cases reported since June 2020 have been in the North Jutland Region. The SARS-CoV-2 variants detected in these cases were part of at least five closely-related clusters; each cluster was characterised by a specific mink-related variant, identified in humans and animals from infected mink farms. Denmark has implemented robust response measures to control the outbreaks in mink and decrease the spill-over between the human and the animal reservoir.
One of the clusters (Cluster 5), which was reported as circulating in August and September 2020, is related to a variant with four genetic changes, three substitutions and one deletion, in the spike (S) protein. Since the S protein contains the receptor-binding domain, and is a major target for immune response, such mutations could, in theory, have implications for viral fitness (ability to infect humans and animals), transmissibility, and antigenicity. As a consequence, the evolution of viruses with increasing changes in functional domains of the S protein could affect treatment, certain diagnostic tests and virus antigenicity. It could also have an impact on the effectiveness of developed vaccine candidates, and possibly require them to be updated. Investigations and studies are ongoing to clarify the extent of these possible implications.